JP2023142713A - Control device of internal combustion engine - Google Patents

Abstract

To suppress increase of discharge of harmful substances, by enhancing temperature rise and activation of a catalyst at a time immediately after cold start of an internal combustion engine.SOLUTION: A control device of an internal combustion engine for controlling the internal combustion engine including a plurality of cylinders 1 and joining gases discharged from each of the cylinders in an exhaust passage 4 to flow into the same exhaust purification catalyst 41, is constituted to adjust an amount of a fuel to be injected to a certain cylinder 1 so that an air fuel ratio of the gas discharged from the cylinder 1 becomes richer than a stoichiometric air-fuel ratio at a timing immediately after cold start of the internal combustion engine, to adjust an amount of a fuel to be injected to the cylinder 1 so that an air fuel ratio of the gas discharged from the other cylinder 1 becomes leaner than the stoichiometric air-fuel ratio, and to control the air fuel ratio of the total of the gases discharged from these cylinders 1 to the stoichiometric air-fuel ratio or vicinity thereof.SELECTED DRAWING: Figure 3

Description

The present invention relates to a control device that controls the operation of an internal combustion engine installed in a vehicle or the like.

A three-way catalyst is installed in the exhaust passage of an internal combustion engine, which oxidizes/reduces harmful substances HC, CO, and _NOx contained in gases exhausted from the cylinders to render them harmless. This type of catalyst has the ability to store excess oxygen (O ₂ storage capacity) when gas with a lean air-fuel ratio flows in. Then, when gas with a rich air-fuel ratio flows in, the stored oxygen is released. Thereby, NO _x contained in the air-fuel ratio lean gas can be appropriately reduced, and HC and CO contained in the air-fuel ratio rich gas can be appropriately oxidized.

In order to efficiently purify all of HC, CO, and _NOx , it is necessary to keep the air-fuel ratio of the gas within a certain range near the stoichiometric air-fuel ratio. For this purpose, it is customary to install an air-fuel ratio sensor on the exhaust passage of an internal combustion engine and perform feedback control to make the air-fuel ratio detected by the sensor follow a required target value (for example, the following patent (see literature).

Japanese Patent Application Publication No. 2021-139340

Immediately after the cold start of the internal combustion engine, the temperature of the exhaust purifying catalyst also decreases. In order to maintain the high performance of the catalyst in purifying harmful substances, it is desirable to raise the temperature of the catalyst as quickly as possible.

An objective of the present invention is to promote temperature rise and activation of a catalyst immediately after a cold start of an internal combustion engine, and to suppress an increase in emissions of harmful substances.

The present invention controls an internal combustion engine that includes a plurality of cylinders and causes gas discharged from each cylinder to flow into the same exhaust purification catalyst through an exhaust passage. adjusting the amount of fuel injected to the some of the cylinders so that the air-fuel ratio of the gas discharged from some of the plurality of cylinders is richer than the stoichiometric air-fuel ratio, and Adjusting the amount of fuel injected to the other cylinders so that the air-fuel ratio of gas discharged from the other cylinders different from the some cylinders is leaner than the stoichiometric air-fuel ratio, A control device for an internal combustion engine is configured to control the total air-fuel ratio of gas discharged from a cylinder and the other cylinders to be at or near the stoichiometric air-fuel ratio.

More specifically, the air-fuel ratio of the gas discharged from the cylinder farthest from the exhaust purification catalyst is made different from the air-fuel ratio of the gas discharged from the cylinder closest to the exhaust purification catalyst. . In particular, the air-fuel ratio of the gas discharged from the cylinder farthest from the exhaust purification catalyst is richer than the stoichiometric air-fuel ratio, and the air-fuel ratio of the gas discharged from the cylinder closest to the exhaust purification catalyst is set to be richer than the stoichiometric air-fuel ratio. It is conceivable to make the air-fuel ratio leaner than the stoichiometric air-fuel ratio.

According to the present invention, it is possible to promote the temperature rise and activation of the catalyst immediately after a cold start of the internal combustion engine, and to suppress an increase in the discharge of harmful substances.

1 is a diagram showing a schematic configuration of an internal combustion engine and a control device in an embodiment of the present invention. FIG. 3 is a flowchart showing an example of a procedure of processing executed by the control device for an internal combustion engine according to the embodiment according to a program. FIG. 3 is a diagram showing an example of air-fuel ratio control for early warm-up of a catalyst by the internal combustion engine control device of the embodiment.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an overview of a vehicle internal combustion engine in this embodiment. The internal combustion engine in this embodiment is a spark ignition four-stroke gasoline engine, and includes a plurality of cylinders 1 (for example, a three-cylinder engine; one of them is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 is provided for each cylinder 1 to inject fuel toward the intake port. Further, a spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 causes a spark discharge between a center electrode and a ground electrode upon application of an induced voltage generated in an ignition coil. The ignition coil is integrally built into the coil case together with the igniter, which is a semiconductor switching element.

The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from upstream.

The exhaust passage 4 for discharging exhaust gas guides exhaust gas generated by burning fuel in the cylinders 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and a three-way catalyst 41 for exhaust purification are arranged on the exhaust passage 4. Upstream and downstream of the catalyst 41 in the exhaust passage 4, air-fuel ratio sensors 43 and 44 are provided to detect the air-fuel ratio of gas flowing through the exhaust passage 4. The air-fuel ratio sensors 43 and 44 may each be an _O2 sensor that has an output characteristic that is non-linear with respect to the air-fuel ratio of gas, or a linear A/F sensor that has an output characteristic that is proportional to the air-fuel ratio of gas. Good too. In this embodiment, it is assumed that both the air-fuel ratio sensor 43 upstream of the catalyst 41 and the air-fuel ratio sensor 44 downstream of the catalyst 41 are O ₂ sensors.

The exhaust gas recirculation device 2 includes an external EGR passage 21 that communicates the exhaust passage 4 and the intake passage 3, an EGR cooler 22 provided on the EGR passage 21, and an EGR passage 21 that opens and closes the EGR passage 21. The element includes an EGR valve 23 that controls the flow rate of EGR gas flowing through the passage 21. The entrance of the EGR passage 21 is connected to a predetermined location downstream of the catalyst 41 in the exhaust passage 4 . The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3 (in particular, the surge tank 33 or the intake manifold 34).

An ECU (Electronic Control Unit) 0, which is a control device for an internal combustion engine in this embodiment, is a microcomputer system including a processor, a memory, an input interface, an output interface, and the like. The ECU0 may include a plurality of ECUs or controllers connected to each other so as to be communicable via a telecommunication line such as a CAN (Controller Area Network).

The input interface of ECU0 includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed (or wheel rotation speed), and detects the rotation angle and engine rotation speed of the crankshaft, which is the output shaft of the internal combustion engine. A crank angle signal b output from a crank angle sensor that detects the amount of depression of the accelerator pedal by the driver or the opening degree of the throttle valve 32 from a sensor that detects the accelerator opening degree (so to speak, the required engine load factor or engine torque). The accelerator opening signal c that is output, the intake temperature and intake pressure that are output from the temperature and pressure sensor that detects the intake air temperature and intake pressure in the intake passage 3 (particularly the surge tank 33 or intake manifold 34) connected to the cylinder 1. signal d, a cooling water temperature signal e outputted from a water temperature sensor that detects the cooling water temperature of the internal combustion engine, and an air-fuel ratio signal outputted from an air-fuel ratio sensor 43 that detects the air-fuel ratio of gas on the upstream side of the catalyst 41 for exhaust purification. f, an air-fuel ratio signal g output from an air-fuel ratio sensor 44 that detects the air-fuel ratio of gas on the downstream side of the catalyst 41, an atmospheric pressure signal h output from an atmospheric pressure sensor that detects atmospheric pressure, etc. are input.

From the output interface of the ECU 0, an ignition signal i is sent to the igniter of the spark plug 12 of the internal combustion engine, a fuel injection signal j is sent to the injector 11, and an opening operation signal k is sent to the motor that drives the valve body of the throttle valve 32. , outputs an opening operation signal l, etc. to the motor that drives the valve body of the EGR valve 23.

The processor of ECU0 interprets and executes programs stored in memory in advance, calculates operating parameters, and controls the operation of the internal combustion engine. The ECU0 acquires various information a, b, c, d, e, f, g, and h necessary for operational control of the internal combustion engine and the vehicle through the input interface, and calculates the required fuel injection amount, fuel injection timing (one time The engine determines operating parameters such as (including the number of fuel injections per combustion), fuel injection pressure, ignition timing (including the number of ignitions per one combustion), required EGR rate (or EGR gas amount), etc. ECU0 applies various control signals i, j, k, l corresponding to operating parameters via an output interface.

In determining the amount of fuel to be injected from the injector 11, the ECU 0 first calculates the amount of air (fresh air) taken into the cylinder 1 from the intake pressure, intake temperature, engine speed, required EGR rate, etc. A basic injection amount TP commensurate with this is determined. The basic injection amount TP is the amount of fuel required to realize the target air-fuel ratio, which is proportional to the intake air amount. The target air-fuel ratio is usually the stoichiometric air-fuel ratio or a value near it. However, as will be described later, in this embodiment, the amount of fuel injected from the injector 11 for each cylinder 1, and even the air-fuel ratio of the air-fuel mixture filled into each cylinder 1, may vary greatly and unevenly. .

When performing feedback control of the air-fuel ratio of the air-fuel mixture, the basic injection amount TP is corrected using a feedback correction coefficient FAF that is determined according to the air-fuel ratio of the gas upstream and/or downstream of the catalyst 41 in the exhaust passage 4. do. The feedback correction coefficient FAF is a positive number centered around 1, and is adjusted according to the deviation between the gas air-fuel ratio actually measured via the air-fuel ratio sensors 43 and 44 and the target air-fuel ratio, so that the actual measured air-fuel ratio becomes the target air-fuel ratio. It increases when the air-fuel ratio is lean with respect to the air-fuel ratio, and decreases when the measured air-fuel ratio is rich with respect to the target air-fuel ratio.

Then, the final fuel injection time T is calculated by taking into consideration various correction coefficients K determined according to the operating status of the internal combustion engine, environmental conditions, etc., and the invalid injection time TAUV of the injector 11. The fuel injection time T is
T=TP×FAF×K+TAUV
becomes. The ECU0 energizes the injector 11 with a signal j for a fuel injection time T, opens the injector 11, and injects fuel.

Therefore, as shown in FIG. 2, the ECU 0 of the present embodiment is configured to operate the engine immediately after the cold start of the internal combustion engine, or depending on whether the warm-up of the internal combustion engine and the catalyst has been completed to a certain extent after that period. (Step S1), and control of the amount of fuel injected into each cylinder 1 from the injector 11 facing each cylinder 1 is changed (Steps S2, S3).

The period immediately after a cold start of the internal combustion engine, for example, the temperature of the cooling water of the internal combustion engine is a low temperature below a predetermined value, the temperature of the catalyst 41 is a low temperature below a predetermined value, or the time elapsed after a cold start. When the number of cycles is less than a predetermined value (step S1), as illustrated in FIG. 3, the air-fuel ratio of the air-fuel mixture filled in each cylinder 1 is not made uniform among the cylinders 1, but varies greatly. (Step S2).

When using gasoline as fuel, the stoichiometric air-fuel ratio is approximately 14.6. In step S2, the ECU 0 controls the injector 11 for the cylinder 1 to make the air-fuel ratio of the air-fuel mixture in the cylinder 1 that is farthest from the catalyst 41 to about 12.6, which is excessively richer than the stoichiometric air-fuel ratio. Increase the amount of fuel injected from. On the other hand, the air-fuel ratio of the mixture in the cylinder 1 closest to the catalyst 41 and the intermediate cylinder 1 is set to approximately 15.9, which is excessively leaner than the stoichiometric air-fuel ratio. The amount of fuel injected from the injector 11 is reduced.

The total air-fuel ratio of the gases discharged from each cylinder 1 listed above is set to be the stoichiometric air-fuel ratio or a value close to it, for example, about 14.8. The stoichiometric air-fuel ratio of 14.8 is slightly leaner than the stoichiometric air-fuel ratio of 14.6 for gasoline fuel, but this is because harmful substances HC are easily discharged immediately after the internal combustion engine is cold-started. In order to oxidize HC in the catalyst 41 and render it harmless, it is advantageous to make the atmosphere inside the catalyst 41 somewhat leaner.

In step S2, the ignition timing may be made equal for each cylinder 1, or may be made different for each cylinder 1. Generally, immediately after a cold start of the internal combustion engine, the ignition timing is corrected to be retarded than normal in order to raise the temperature of the gas discharged from the cylinder 1 and flowing into the catalyst 41. However, the ignition timing may be advanced in the cylinder 1 in which the air-fuel mixture is difficult to burn compared to the cylinder 1 in which the air-fuel mixture is easy to burn.

After that, if the temperature of the cooling water of the internal combustion engine rises to a predetermined value or more, the temperature of the catalyst 41 rises to a predetermined value or more, or the time or number of cycles that has passed since the cold start exceeds a predetermined value. (Step S1), the routine shifts to normal control, that is, control for equalizing the air-fuel ratio of the air-fuel mixture filled in each cylinder 1 (Step S3). In step S3, for example, the amount of fuel injected from the injector 11 to each cylinder 1 is controlled so that the air-fuel ratio of the air-fuel mixture in each cylinder 1 is approximately 14.6, which is close to the stoichiometric air-fuel ratio.

According to this embodiment, immediately after the cold start of the internal combustion engine, the air-fuel ratio of the gas that sequentially flows into the catalyst 41 from each cylinder 1 increases or decreases greatly, and a large amount of reaction heat is generated in the catalyst 41. Early temperature rise is promoted. In addition, the amount of harmful substances discharged can be further reduced.

Note that the present invention is not limited to the embodiments detailed above. The specific configuration of each part, processing procedure, etc. can be variously modified without departing from the spirit of the present invention.

0...Control unit (ECU)
1...Cylinder 11...Injector 4...Exhaust passage 41...Catalyst

Claims (3)

It controls an internal combustion engine that includes multiple cylinders and causes gas exhausted from each cylinder to flow into the same exhaust purification catalyst through an exhaust passage.
Immediately after the cold start of the internal combustion engine,
adjusting the amount of fuel injected to the some of the cylinders so that the air-fuel ratio of gas discharged from some of the plurality of cylinders is richer than the stoichiometric air-fuel ratio;
and adjusting the amount of fuel injected to the other cylinders so that the air-fuel ratio of gas discharged from the other cylinders different from the some of the cylinders is leaner than the stoichiometric air-fuel ratio;
A control device for an internal combustion engine that controls the total air-fuel ratio of gas discharged from the some cylinders and the other cylinders to be at or near the stoichiometric air-fuel ratio. The internal combustion engine according to claim 1, wherein the air-fuel ratio of the gas discharged from the cylinder furthest from the exhaust purification catalyst is different from the air-fuel ratio of the gas discharged from the cylinder closest to the exhaust purification catalyst. Engine control equipment. The air-fuel ratio of gas discharged from the cylinder farthest from the exhaust purification catalyst is set to be richer than the stoichiometric air-fuel ratio, and the air-fuel ratio of gas discharged from the cylinder closest to the exhaust purification catalyst is set to be richer than the stoichiometric air-fuel ratio. 3. The control device for an internal combustion engine according to claim 2, wherein the fuel ratio is leaner than the fuel ratio.

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